System Construction Of Pickering Emulsions And Microemulsions And Their Impact On Enhanced Recovery

As the main technology to improve recovery from medium and high permeability reservoirs in China,chemical oil flooding technology is widely used in old oil fields with high water content,and a large number of studies have shown that the emulsification phenomenon during chemical oil flooding is crucial to its successful application.However,it is difficult to form microemulsion flooding in chemical oil flooding that can solubilise oil and water in large quantities,while the emulsion formed by the interaction between the crude oil and the surfactant in the high water content phase has a low oil content and is less stable,making it difficult to achieve significant recovery improvements.Therefore,exploring the conditions for the formation of microemulsion in the chemical oil flooding process and finding a efficient and stable emulsion system are essential to further improve the quality and efficiency of chemical oil flooding technology.In this thesis,the optimal formulation of medium-phase microemulsions is selected and statically evaluated by orthogonal experiments,and the effect of changes in salinity and alcohol on the phase state of the microemulsion system is investigated using the phase diagram method.The formulation of Pickering emulsion is optimised and the performance differences between different formulations are analysed by means of laser confocal and rheological tests;and based on micro-visualisation experiments,the oil repelling effect and repelling mechanism of micro-emulsions and emulsions at the porethroat scale are investigated,and the effect of micro-emulsions and emulsions on enhanced recovery is tested by core repelling experiments.It is shown that 3.5% surfactant A,7% n-butanol and 3.5% sodium carbonate formed the best intermediate phase microemulsions with a concentrated particle size distribution of 10-100 nm,and that the microemulsions formed could be converted from Winsor I to Winsor III and then to Winsor II by changing the salinity and alcohol.The nanoparticles are added to the oil-water interface to form a Pickering emulsion,which is stable for more than 12 h.The micro-visualisation experiments show a final recovery of 68.8% for Pickering emulsion flooding and 87.1% for in-situ formed microemulsion flooding with the best mobilisation of the micro inhomogeneous residual oil.In core replacement experiments using simulated oil and crude oil,the final recovery from in-situ formed microemulsion flooding is 57.5%,continuing to improve recovery by 19.7 percentage points on top of the water flooding and 3.4 percentage points higher than the emulsion flooding.This work shows that both Pickering emulsion flooding and in-situ formed microemulsion flooding can significantly improve recovery after water flooding,which can provide a reference for the development of chemical oil flooding technology.